GNSS vs GPS | Difference between GNSS and GPS
This page compares GNSS vs GPS and mentions difference between GNSS and GPS terminologies.
Introduction: Both GPS and GNSS terms are associated with satellite navigation systems used to determine location and elevation of the devices. These technologies are employed in many consumer electronics, automotive applications, marine guidance, surveying, cellular handsets etc.
GPS is one of the many GNSS systems used across the globe. GNSS is umbrella term which includes GPS, GLONASS, GALILEO, COMPASS etc.
There are three main components in GNSS architecture as shown in the figure viz. space segment, control segment and user segment.
• Space Segment : It consists of satellites around the Earth. They continuously transmit radio signals towards the Earth.
• Ground Control Systems : They are used to assure accuracy of the system. There are about 5 number of control stations. They enable information on the Earth to be transmitted to the satellites such as updates, fine turning etc. COntrol stations continuously track the satellites and update the positions of each of the satellites.
• GPS or GNSS receivers : The radio signals are picked up by these receivers to determine location. This is possible as GPS receiver knows about time required by signal to travel from satellite to the receiver. At least four satellites are required to determine exact location and elevation by GPS receivers.
➨Distance = time x velocity
➨Using above formula, GPS receiver calculates exact distance from the satellite
• GPS refers to contellation of navigation satellites which are associated with american system.
• GPS was developed by US Department of Defense at the cost of greater than $ 12 billion.
• Initially only GPS was available for long time. Hence all the components such as satellites, receivers etc. were referred as GPS.
• After few years, other GNSS systems have been developed.
• GPS consists of 24 to 32 MEO (Medium Earth Orbit) satellites orbiting in six planes at the altitude of approx. 11000 nautical miles.
• Total number of satellites vary due to replacement and newly introduced satellites.
• GPS is most utilized satellite navigation system across the world.
There are two types of GPS signals.
P-code (Precise code) : Only available to military and some public officials, very precise and not degraded
C-code (Civilian code) : Less precise, signal can be degraded in times of conflict, GARMIN receivers and all public receivers work with this.
GNSS include all of the following satellite based navigation systems.
• GPS : US, operational since 1994.
• GLONASS : Russian, re-operational since 2010.
• GALILEO : European Union, 2011
• BeiDOU : CHINA, operational in Asia/Pacific since 2000
The other regional GNSS systems include IRNSS (Indian Regional Navigation Satellite System) used in INDIA amd QZSS (Quasi Zenith Satellite System) used in Japan. The figure depicts the difference between GNSS and GPS systems.
There are three different grades of GNSS receivers based on their accuracy, usage and cost.
Recreational Grade GNSS : • Accurate within 5 meters • lowest cost • suitable for hunting, recreational, some businesses etc.
Mapping Grade GNSS : • Accurate within 1 meters • medium cost • Suitable for natural resources, city planning etc.
Survey Grade GNSS : • Accurate within 1 cm • higher cost • Suitable for building bridges etc.
Tabular comparison between GNSS and GPS
Following table mentions comparison between GNSS and GPS terms.
|• Full form||Global Navigation Satellite System||Global Positioning system|
|• Number of Satellites||Utilizes about 89 total satellites from all the four satallite systems e.g. GPS, GLONASS, GALILEO and BeiDou.||Utilizes about 24-32 satellites|
|• Coverage||Wider on global or regional basis as it composed of multiple satellite systems across US, Russia, Europe, China, INDIA and Japan.||Limited to GPS satellite range|
|• Types or grades||Recreational , Mapping, Survey||P-code, C-code|
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